1. Field of the Invention
The present invention relates generally to a semiconductor device and a method of manufacturing the same, more particularly, to a semiconductor device with self-aligned contacts and a method of manufacturing the same.
2. Description of the Prior Art
The semiconductor industry has always strived to achieve smaller feature sizes. For example, the size of transistors such as planar transistors has steadily decreased through advances in process development and the need to increase feature density. Current scaling employs 28 nm technologies with development also progressing towards 20 nm and beyond technologies (e.g., 14 nm technologies). Moreover, replacement gate process flows are developed and becoming more commonly utilized as they can avoid certain problems found in gate first processes. For example, replacement metal gate (RMG) processes may avoid problems associated with the stability of the work function material used in the gates.
Most contact processes would suffer from alignment issues when making trench contacts and/or local interconnect connections to the gate. Conventional contact processes are not self-aligned and can easily fail from misalignment during processing. It may also be difficult to pattern bidirectional local interconnect and/or reduce the number of interface layers from the local interconnect to either the gate or the source/drain of the gate.
Moreover, forming reliable contact structures for semiconductor devices would become more difficult as feature sizes have decreased and device densities on a chip have increased. For example, the aspect ratio (ratio of depth to width) of contact structures increases as device density increases. As a result, it is becoming increasingly difficult to perform contact etching to a required depth without over-etching in a lateral direction.
To solve some of above-mentioned misalignment and over-etching issues, process flows have been made that attempt to create a self-aligned trench contact that extends above the gate to allow less complex local interconnect flow. Self-aligned production methods make it possible to meet the requirements for smaller structures while at the same time fulfilling tolerance ranges to be complied with.
Such self-aligned contact process flows, however, are typically very complex, have many resistive interfaces, and have high manufacturing costs due to the complex process flow. Additionally, there is a low manufacturing margin for misalignments or other errors due to the complexity of the processes as these processes may have severely restrictive design and/or alignment rules. Thus, there is a need for a method to self-align trench contacts to the sources/drains and extend the trench contacts above the gates.